Add Stock Tracking endpoint to Inventory

Adds GET /client/inventory/stock-movements, a unified read-only ledger
flattening every GRN line, sale line and return across all products
into one shape for the new Stock Tracking tab's table.

Controllers/InventoryController.cs

@@ -170,5 +170,12 @@ namespace Fitness_core_BE.Controllers
                 notes = request.Notes,
                 returnedAt = request.ReturnedAt?.ToString("o")
             }, HttpContext));
+
+        [CustomMiddleware]
+        [TenantResolution]
+        [RequiresPermission("inventory")]
+        [HttpGet("stock-movements")]
+        public async Task<ActionResult<ApiResponse<object>>> GetStockMovements()
+            => Response(await _inventoryService.GetStockMovements(new { }, HttpContext));
     }
 }

DTOs/Inventory/InventoryDtos.cs

@@ -85,6 +85,27 @@ namespace Fitness_core_BE.DTOs.Inventory
         public List<SaleItemDto> Items { get; set; } = [];
     }
 
+    /// <summary>One row in the Stock Tracking tab's unified ledger -- every GRN line, sale line
+    /// and return across every product, flattened into one shape for a single filterable table.
+    /// Not persisted; built on read from GRNs/Sales/Returns.</summary>
+    public class StockMovementDto
+    {
+        /// <summary>"GRN" | "Sale" | "Return".</summary>
+        public string Type { get; set; } = string.Empty;
+        public Guid ProductId { get; set; }
+        public string ProductName { get; set; } = string.Empty;
+        /// <summary>The GRN/Sale number this line belongs to, or the return's Category label.</summary>
+        public string Reference { get; set; } = string.Empty;
+        /// <summary>Only set for Type == "Return" -- the write-off/return category.</summary>
+        public string? Category { get; set; }
+        /// <summary>Signed: positive for a GRN or a CustomerReturn (stock in), negative for a
+        /// Sale or any other return category (stock out).</summary>
+        public decimal QuantityChange { get; set; }
+        /// <summary>This line's monetary value -- a GRN/Sale line's LineTotal, or a return's Amount.</summary>
+        public decimal Amount { get; set; }
+        public DateTime Date { get; set; }
+    }
+
     public class StockReturnDto
     {
         public Guid StockReturnId { get; set; }

Interfaces/Services/IInventoryService.cs

@@ -22,5 +22,7 @@ namespace Fitness_core_BE.Interfaces.Services
         Task<object> CreateStockReturn(object payload, HttpContext httpContext);
         Task<object> GetStockReturns(object payload, HttpContext httpContext);
         Task<object> GetStockReturnById(object payload, HttpContext httpContext);
+
+        Task<object> GetStockMovements(object payload, HttpContext httpContext);
     }
 }

Services/InventoryService.cs

@@ -576,6 +576,67 @@ namespace Fitness_core_BE.Services
             return MapToDto(stockReturn);
         }
 
+        // --- Stock Tracking (unified ledger, new) ---
+
+        /// <summary>Every GRN line, sale line and return across every product, flattened into one
+        /// shape for the Stock Tracking tab's table. Built from the same three already-tenant-
+        /// scoped reads the GRN/Sales/Returns tabs use -- no new repository queries needed, and
+        /// the dataset is small enough (a single gym's "simple inventory") that filtering happens
+        /// client-side rather than via query params.</summary>
+        public async Task<object> GetStockMovements(object payload, HttpContext httpContext)
+        {
+            var clientId = await _userRoleHelper.GetClientId(DataExtractor.GetUserIdFromContext(httpContext));
+
+            var grns = await _inventoryRepository.GetGrns(clientId);
+            var sales = await _inventoryRepository.GetSales(clientId);
+            var returns = await _inventoryRepository.GetStockReturns(clientId);
+
+            var movements = new List<StockMovementDto>();
+
+            foreach (var g in grns)
+                foreach (var i in g.Items)
+                    movements.Add(new StockMovementDto
+                    {
+                        Type = "GRN",
+                        ProductId = i.FKProductId,
+                        ProductName = i.Product?.Name ?? string.Empty,
+                        Reference = g.GrnNumber,
+                        QuantityChange = i.Quantity,
+                        Amount = i.LineTotal,
+                        Date = g.ReceivedAt
+                    });
+
+            foreach (var s in sales)
+                foreach (var i in s.Items)
+                    movements.Add(new StockMovementDto
+                    {
+                        Type = "Sale",
+                        ProductId = i.FKProductId,
+                        ProductName = i.Product?.Name ?? string.Empty,
+                        Reference = s.SaleNumber,
+                        QuantityChange = -i.Quantity,
+                        Amount = i.LineTotal,
+                        Date = s.SoldAt
+                    });
+
+            foreach (var r in returns)
+                movements.Add(new StockMovementDto
+                {
+                    Type = "Return",
+                    ProductId = r.FKProductId,
+                    ProductName = r.Product?.Name ?? string.Empty,
+                    Reference = r.Sale?.SaleNumber ?? r.Grn?.GrnNumber ?? r.Category,
+                    Category = r.Category,
+                    // CustomerReturn is the one category that adds back to stock -- see
+                    // StockReturn's doc comment.
+                    QuantityChange = r.Category == "CustomerReturn" ? r.Quantity : -r.Quantity,
+                    Amount = r.Amount,
+                    Date = r.ReturnedAt
+                });
+
+            return movements.OrderByDescending(m => m.Date).ToList();
+        }
+
         /// <summary>Staff optionally picking an existing registered member to attach to a sale
         /// (search-and-pick, not free-typed) -- purely for identification, mirrors
         /// BookingService.ResolveOptionalCustomerLinkAsync exactly.</summary>